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template_lapack_larf.h
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1 /* Ergo, version 3.8, a program for linear scaling electronic structure
2  * calculations.
3  * Copyright (C) 2019 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
4  * and Anastasia Kruchinina.
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18  *
19  * Primary academic reference:
20  * Ergo: An open-source program for linear-scaling electronic structure
21  * calculations,
22  * Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
23  * Kruchinina,
24  * SoftwareX 7, 107 (2018),
25  * <http://dx.doi.org/10.1016/j.softx.2018.03.005>
26  *
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29 
30  /* This file belongs to the template_lapack part of the Ergo source
31  * code. The source files in the template_lapack directory are modified
32  * versions of files originally distributed as CLAPACK, see the
33  * Copyright/license notice in the file template_lapack/COPYING.
34  */
35 
36 
37 #ifndef TEMPLATE_LAPACK_LARF_HEADER
38 #define TEMPLATE_LAPACK_LARF_HEADER
39 
40 
41 template<class Treal>
42 int template_lapack_larf(const char *side, const integer *m, const integer *n, const Treal *v,
43  const integer *incv, const Treal *tau, Treal *c__, const integer *ldc,
44  Treal *work)
45 {
46 /* -- LAPACK auxiliary routine (version 3.0) --
47  Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
48  Courant Institute, Argonne National Lab, and Rice University
49  February 29, 1992
50 
51 
52  Purpose
53  =======
54 
55  DLARF applies a real elementary reflector H to a real m by n matrix
56  C, from either the left or the right. H is represented in the form
57 
58  H = I - tau * v * v'
59 
60  where tau is a real scalar and v is a real vector.
61 
62  If tau = 0, then H is taken to be the unit matrix.
63 
64  Arguments
65  =========
66 
67  SIDE (input) CHARACTER*1
68  = 'L': form H * C
69  = 'R': form C * H
70 
71  M (input) INTEGER
72  The number of rows of the matrix C.
73 
74  N (input) INTEGER
75  The number of columns of the matrix C.
76 
77  V (input) DOUBLE PRECISION array, dimension
78  (1 + (M-1)*abs(INCV)) if SIDE = 'L'
79  or (1 + (N-1)*abs(INCV)) if SIDE = 'R'
80  The vector v in the representation of H. V is not used if
81  TAU = 0.
82 
83  INCV (input) INTEGER
84  The increment between elements of v. INCV <> 0.
85 
86  TAU (input) DOUBLE PRECISION
87  The value tau in the representation of H.
88 
89  C (input/output) DOUBLE PRECISION array, dimension (LDC,N)
90  On entry, the m by n matrix C.
91  On exit, C is overwritten by the matrix H * C if SIDE = 'L',
92  or C * H if SIDE = 'R'.
93 
94  LDC (input) INTEGER
95  The leading dimension of the array C. LDC >= max(1,M).
96 
97  WORK (workspace) DOUBLE PRECISION array, dimension
98  (N) if SIDE = 'L'
99  or (M) if SIDE = 'R'
100 
101  =====================================================================
102 
103 
104  Parameter adjustments */
105  /* Table of constant values */
106  Treal c_b4 = 1.;
107  Treal c_b5 = 0.;
108  integer c__1 = 1;
109 
110  /* System generated locals */
111  integer c_dim1, c_offset;
112  Treal d__1;
113 
114 
115  --v;
116  c_dim1 = *ldc;
117  c_offset = 1 + c_dim1 * 1;
118  c__ -= c_offset;
119  --work;
120 
121  /* Function Body */
122  if (template_blas_lsame(side, "L")) {
123 
124 /* Form H * C */
125 
126  if (*tau != 0.) {
127 
128 /* w := C' * v */
129 
130  template_blas_gemv("Transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1], incv,
131  &c_b5, &work[1], &c__1);
132 
133 /* C := C - v * w' */
134 
135  d__1 = -(*tau);
136  template_blas_ger(m, n, &d__1, &v[1], incv, &work[1], &c__1, &c__[c_offset],
137  ldc);
138  }
139  } else {
140 
141 /* Form C * H */
142 
143  if (*tau != 0.) {
144 
145 /* w := C * v */
146 
147  template_blas_gemv("No transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1],
148  incv, &c_b5, &work[1], &c__1);
149 
150 /* C := C - w * v' */
151 
152  d__1 = -(*tau);
153  template_blas_ger(m, n, &d__1, &work[1], &c__1, &v[1], incv, &c__[c_offset],
154  ldc);
155  }
156  }
157  return 0;
158 
159 /* End of DLARF */
160 
161 } /* dlarf_ */
162 
163 #endif
mat::side
side
Definition: Matrix.h:75
template_blas_ger
int template_blas_ger(const integer *m, const integer *n, const Treal *alpha, const Treal *x, const integer *incx, const Treal *y, const integer *incy, Treal *a, const integer *lda)
Definition: template_blas_ger.h:42
template_blas_gemv
int template_blas_gemv(const char *trans, const integer *m, const integer *n, const Treal *alpha, const Treal *a, const integer *lda, const Treal *x, const integer *incx, const Treal *beta, Treal *y, const integer *incy)
Definition: template_blas_gemv.h:43
template_blas_lsame
logical template_blas_lsame(const char *ca, const char *cb)
Definition: template_blas_common.cc:46
integer
int integer
Definition: template_blas_common.h:40
template_lapack_larf
int template_lapack_larf(const char *side, const integer *m, const integer *n, const Treal *v, const integer *incv, const Treal *tau, Treal *c__, const integer *ldc, Treal *work)
Definition: template_lapack_larf.h:42